If this list is not empty, the package is marked as "insecure", meaning that it cannot be built or installed unless the environment variable [`NIXPKGS_ALLOW_INSECURE`](#sec-allow-insecure) is set.

## Licenses {#sec-meta-license}

The `meta.license` attribute should preferably contain a value from `lib.licenses` defined in [`nixpkgs/lib/licenses.nix`](https://github.com/NixOS/nixpkgs/blob/master/lib/licenses.nix), or in-place license description of the same format if the license is unlikely to be useful in another expression.

Although it’s typically better to indicate the specific license, a few generic options are available:

### `lib.licenses.free`, `"free"` {#lib.licenses.free-free}

Catch-all for free software licenses not listed above.

### `lib.licenses.unfreeRedistributable`, `"unfree-redistributable"` {#lib.licenses.unfreeredistributable-unfree-redistributable}

Unfree package that can be redistributed in binary form. That is, it’s legal to redistribute the *output* of the derivation. This means that the package can be included in the Nixpkgs channel.

Sometimes proprietary software can only be redistributed unmodified. Make sure the builder doesn’t actually modify the original binaries; otherwise we’re breaking the license. For instance, the NVIDIA X11 drivers can be redistributed unmodified, but our builder applies `patchelf` to make them work. Thus, its license is `"unfree"` and it cannot be included in the Nixpkgs channel.

### `lib.licenses.unfree`, `"unfree"` {#lib.licenses.unfree-unfree}

Unfree package that cannot be redistributed. You can build it yourself, but you cannot redistribute the output of the derivation. Thus it cannot be included in the Nixpkgs channel.

### `lib.licenses.unfreeRedistributableFirmware`, `"unfree-redistributable-firmware"` {#lib.licenses.unfreeredistributablefirmware-unfree-redistributable-firmware}

This package supplies unfree, redistributable firmware. This is a separate value from `unfree-redistributable` because not everybody cares whether firmware is free.

## Source provenance {#sec-meta-sourceProvenance}